This paper describes a completely automated method for generating efficient and competitive interpreters from formal semantics expressed in Rewriting Logic. The semantics are compiled into OCaml code, which then acts as the interpreter for the language being defined. This automatic translation is tested on the semantics of an imperative as well as a functional language, and these generated interpreters are then benchmarked across a number of programs. In all cases the compiled interpreter is faster than directly executing the definition in a Rewriting system with improvements of several orders of magnitude.